ICs, LSIs and LCDs on a semiconductor wafer are usually produced by forming fine electronic circuit patterns on a substrate relying upon the photolithography technology. Concretely speaking, a photoresist is applied onto a substrate wafer on which is formed an insulating film such as of silicon oxide, a wiring layer such as of Al, Cu, Si or Ti, or a low-dielectric interlayer insulating film such as of SOG or a fluorine-contained resin, followed by exposure to light through a mask forming desired patterns and by developing to form a resist pattern at desired portions. Then, the insulating film and the wiring layer or the low-dielectric interlayer insulating film are etched from above the resist pattern, and the resist is removed. In forming the electronic circuit pattern as described above, the photoresist is removed by being washed with a solution for washing residue or by the ashing treatment. The latter ashing treatment is to remove the resist by turning the resist into an ash thereof using energy such as of a plasma. On the surfaces from where the photoresist is removed after the ashing treatment, there remain incompletely ashed products called photoresist ashing residue and side-wall deposit films formed near the side walls of the patterns during the etching without being removed to a sufficient degree. Here, the side-wall deposit films stand for sparingly soluble products formed on the side walls of the photoresist mask or on the side walls of the patterns during the etching step due to complex reactions among the etching gas, photoresist, underlying insulating film, wiring layer, low-dielectric interlayer insulating film and substrate. The side-wall deposit films may often be intentionally formed in order to enhance the anisotropic etching effect, or may be formed against the will.
When the reactive ionic etching (RIE) is conducted, in particular, there are formed side-wall deposit films and incompletely ashed products of photoresist, which dissolve little, to a conspicuous degree. The RIE is a method of conducting the etching by applying a negative voltage to the wafer which is a substrate, and irradiating the reactive gas containing a halogen compound gas such as of carbon fluoride, hydrogen fluoride or hydrogen chloride with a plasma.
The photoresist is degenerated and becomes sparingly soluble even when it is subjected to the ion-injection treatment. Even after the ashing treatment, the incompletely ashed products of the photoresist form to a conspicuous degree. The ion-injection treatment is an operation for injecting ions such as of phosphorus, boron, antimony or arsenic into the resist surface from above the resist in order to form electrically conducting portions in the desired places. Here, the resist works as a mask enabling the ions to be selectively injected into the portions from where the resist is removed.
Inclusive of the photoresist after developing, the incompletely ashed products of photoresist remaining on the surfaces after the ashing treatment and the side-wall deposit films, cause defective contact to the wiring patterns and are, hence, desired to be removed by washing. Therefore, solutions of various organic solvents have been used for washing residues in an attempt to remove the residue inclusive of the photoresist. However, the photoresist to which ions are injected is degenerated. Besides, the photoresist residue after ashing is often a high degree of polymer or has partly been turned into inorganic, and cannot, hence, be removed to a sufficiently degree with the above residue-washing solutions.
Under such circumstances, Japanese Unexamined Patent Publication (Kokai) No. 67632/1999 discloses a residue-washing solution of a composition containing a fluorine compound, a water-soluble organic solvent and the remainder of water. Owing to a system of the fluorine compound and water, the above washing solution works to favorably peel off even the residues containing organic matters in relatively small amounts, and works to prevent the wiring material existing on the to-be-washed surfaces from being corroded since it contains the water-soluble organic solvent in an amount of from 50 to 80% by weight.
However, water is indispensable for the above washing solution to exhibit performance for removing the residue, and room for improvement still remains concerning the corrosion-preventing effect by using the organic solvent only. That is, the layer under the residue to be washed away has not been treated to be corrosion resistant to a sufficient degree. In particular, a problem of corrosion occurs in the metal wiring material such as of aluminum or aluminum alloy, or in the low-dielectric interlayer insulating film such as of SOG.
Concerning the above problem, the above publication proposes adding a surfactant in an attempt to prevent corrosion to a high degree.
However, foam generates by the addition of the surfactant. Adhesion of foam onto the wafer prevents the washing. Besides, when foam is brought out of the system, the surfactant component only decreases selectively in the residue-washing solution, and the effect for preventing the corrosion changes.
A problem still exists in that the residue which has further turned into inorganic due to severe ashing conditions, cannot be completely removed with the above washing solution. This is because, since the washing solution contains a large amount of the organic solvent as a corrosion-preventing agent, the fluorine compound added as a washing component is not allowed to exhibit its washing performance to a sufficient degree.
As a washing solution of a composition using an organic solvent which is a corrosion-preventing agent in limited amounts and using a surfactant as a corrosion-preventing agent, Japanese Unexamined Patent Publication (Kokai) No. 194144/2000 discloses a composition comprising a fluorine compound, an amphoteric surfactant and the remainder of water. This washing solution is capable of favorably removing the residues such as incompletely ashed products of photoresist which are transformed to a considerable degree and side-wall deposit films, causing the insulating film and the wiring layer on the substrate wafer to be corroded little.
Even with the above washing solution, however, a problem remains concerning the generation of foam at the time of washing the residue due to the addition of the amphoteric ionic surfactant.
It has therefore been desired to develop a residue-washing solution which is capable of exhibiting stable and excellent corrosion-preventing ability yet generating foam little even when the ratio of the organic solvent to the water is arbitrarily changed.
In recent years, on the other hand, there has been used a Cu wiring as a Cu damascene process. In this case, the pattern has been formed by grinding the Cu wiring by a method called chemical/mechanical polishing (CMP). After the CMP treatment, there remain, on the substrate, a polishing agent powder such as of alumina or silica as well as powders formed by grinding the substrate, such as of copper oxide, tantalum, tantalum nitride and residues such as of low-dielectric interlayer insulating film and insulating film. Here, most of the residues are inorganic matters which must be removed by strong washing. However, since the underlying wirings, too, are inorganic matters such as metals, corrosion of the underlayers cannot be avoided.
Concerning the problem of corrosion, there have heretofore been used aromatic hydroxy compounds, acetylene alcohols and triazole compounds as corrosion-preventing agents that are to be added to the washing solution. It can therefore be considered to use them as corrosion-preventing agents for the above washing solution. However, the washing solution that is obtained exhibits the corrosion-preventing property only weakly.